Do You Really Need to Replace All 4 Tires on a Subaru?

When it comes to maintaining a Subaru, one question that often arises is whether you need to replace all four tires simultaneously. This matter is significant, especially with the Subaru AWD system, which demands uniform tire diameter and performance for optimal vehicle handling and drivetrain health.

Tire Diameter and the AWD System

The Subaru AWD system, in particular, has specific guidelines regarding the maximum difference in tire diameter. According to these specifications, if you have four brand new or extremely low mileage tires, you may replace just one tire, provided it matches the diameter and, ideally, the exact type as the other three. However, if the tires are all higher mileage, there is a high likelihood of exceeding the specified diameter allowance, necessitating a full replacement.

Factors Influencing Tire Replacement

The decision to replace all four tires on a Subaru—or any vehicle—hinges on several key factors:

Tread Wear: If the tread depth on all four tires is significantly worn, it is advisable to replace them together to ensure balanced handling and traction. Tires with varying tread depths can lead to inconsistent performance and potential safety risks. All-Wheel Drive AWD: Subaru vehicles are renowned for their AWD systems. Uneven tire wear can put strain on the drivetrain, potentially leading to mechanical issues. Replacing all four tires is often recommended to maintain uniformity and prevent excessive wear that could affect the drivetrain. Age of Tires: Even if the tread appears acceptable, tires should be replaced every six years due to rubber degradation. Older tires may no longer provide optimal performance and safety. This is particularly true for AWD vehicles where tire uniformity is crucial. Damage: If one tire is severely damaged (e.g., a sidewall puncture), it is often recommended to replace all four tires for consistency, especially in AWD vehicles. This ensures that the drivetrain is not inconsistently stressed and maintains balanced performance. Manufacturer Recommendations: Always consult the owner's manual for specific guidance on tire replacement for your Subaru model. The manufacturer's recommendations are tailored to the specific characteristics and requirements of your vehicle.

In summary, while it is not always essential to replace all four tires, it is often the best practice for maintaining vehicle performance and safety, especially with Subaru's AWD systems. If you are unsure, consulting a tire professional or your vehicle's manual is a reliable course of action.

Single Tire Replacement Guidelines

Replacing just one tire on an AWD or 4x4 vehicle is possible only if the tread wear on that tire does not exceed 2/32 of an inch. This limit is set to prevent significant size differences in the tires, which could cause traction differences and undue stress on the drivetrain. Adhering to this guideline ensures that your vehicle maintains optimal performance and safety.